Metal-free Michael addition initiated multicomponent oxidative cyclodehydration route to polysubstituted pyridines from 1,3-dicarbonyls

Abstract

A simple metal-free, step-economic and selective access to pyridines from readily available substrates is reported, involving a flexible 4 A molecular sieves promoted Michael addition initiated domino three-component reaction between a 1,3-dicarbonyl, a Michael acceptor and a synthetic equivalent of ammonia.

Dual Heterogeneous Catalysis for a Regioselective Three‐ Component Synthesis of Bi‐ and Tri(hetero)arylpyridines

“…[25] Among these methodologies, we recently reported preliminary results on the regioselective metal-free three-component access to pyridine derivatives (Scheme 1). [26] This flexible environmentally-friendly strategy involved the direct open flask condensation of 1,3-dicarbonyls 1 with Michael acceptors 2 and ammonium acetate 3 under heterogeneous catalysis by 4 MS in its "classical conditions" (Scheme 1, method A). More recently, we successfully extended this reaction to the first use of b,g-unsaturated-a-keto carbonyl derivatives as Michael acceptors in an MCR.…”

The Application of 4Å Molecular Sieves in Organic Chemical Syntheses: An Overview

“…Then a simple, metal-free, and regioselective method for the preparation of polysubstituted pyridines 78-80 was published involving a MS 4A promoted Michael addition initiated domino three-component reaction between a 1,3-dicarbonyl compound (69, 10, 71, 75), a Michael acceptor (76) and ammonium acetate (77) (Scheme 23). 45 MS 4A acted both as dehydrating agent and as heterogeneous catalyst, as shown in the previous article. Dieses Dokument wurde zum persönlichen Gebrauch heruntergeladen.…”

“…25 In the ytterbium-catalysed reaction, in the absence of MS 4A, reverse enantiofacial selectivity was observed. 26 Scheme 12 Asymmetric 1,3-dipolar cycloadditions of nitrones 39 to 3-(2-alkenoyl)-2-oxazolidinone (40) In 2000, Hirama and co-workers disclosed that the presence of MS 4A considerably affected the enantioselectivity in the chiral TADDOL-Ti complex (45) promoted Diels-Alder reaction of 2-methoxy-5-methyl-1,4-benzoquinone (43) with 1-acetoxy-1,3-butadiene (44). Without MS 4A, the (R)-adduct was formed in 72% ee, whereas in the presence of MS 4A the (S)-enantiomer was obtained in up to 53% ee (Scheme 13).…”

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

“…In this context, Rodriguez’s group successfully established a one-pot three-component reaction between β,γ-unsaturated α-ketoesters, 1,3-dicarbonyl compounds, and ammonium acetate promoted by acid under aerobic conditions [ 37 – 38 ]. Furthermore, Brønsted- and Lewis-acid-catalyzed cyclization reactions between β-enamino esters (derived from β-ketoesters and ammonium acetate) and alkynones/α,β-unsaturated carbonyls/in situ generated α,β-unsaturated ketones (from alkyl ketones) as Michael acceptors to construct a diverse set of nicotinate derivatives were developed by Bohlman–Rahtz [ 39 ], Bagley [ 40 – 41 ] and other groups independently [ 42 – 55 ].…”